The invention relates to hair curlers and more particularly to electrically heated hair curlers.
Electrically heated hair curlers have found wide market acceptance in recent years. In general, these curlers comprise an outer cylindrical shell of a suitable polymer provided with a plurality of fingers extending outwardly from the outer peripheral surface of the shell for grasping hair wound about the shell. One type of curler employing these curlers are heated to a desired temperature, then taken by the user who trains hair about the periphery. The hair is generally kept in contact with the curler for a short period of time to effect curling of the hair. Various ways have been used to heat the curlers but all have certain disadvantages. One type of curler employs, mounted within the shell, a housing which contains a fusible wax. The curler is placed in heat transfer relation with a heating element until the wax melts and is then removed from the heat source and is ready for use. However, since the wax is changed to a liquid, special precautions must be taken to insure a good seal. Further, the time which is required for the curler to be heated is longer than desirable due to the relatively low heat conductivity of the wax. The wax-filled device offers the advantage of being an excellent heat storage means due to the latent heat released during phase change of the wax from liquid to solid upon cooling. Attempts have been made to avoid these disadvantages by using a resistance element in the curler both in the heater and in the heat storing means. This avoids the liquid sealing problem but the warm-up time for the device time is still excessive since a relatively massive resistance element must be employed in order to store the heat for the required time after de-energization. Both of the above types require current controlling devices, such as thermostats. Further, heat distribution along the surface of the curler for both types is relatively non-uniform with a concomitant non-uniform degree of curling for different sections of hair.
Thus it is an object of the invention to obviate the disadvantages of the prior art curlers mentioned above.
Another object of the invention is the provision of a hair curler heater which combines the functions of various components used in prior art devices.
Yet another object is the provision of a simple, reliable, rugged hair curler device, one which provides uniform heating with no hot or cold spots. Another object is the provision of a hair curler heater which has an extremely fast warm-up time along with maintaining its heat for a prolonged period. Yet another advantage is the provision of a hair curler device which needs no thermostats and provides close temperature control.
Other objects and features will be in part apparent and in part pointed out hereinafter.
Briefly, the invention meets the above objects by providing a heat storage means mounted within a hair curler shell in close heat transfer relation with the shell, the heat storage means including a heating element which has a steeply-sloped PTC at temperatures above an anomaly. In one embodiment the heat storage means and the heating element are formed from the same element, an elongated annulus which is coated on the inner and outer peripheral surfaces with a conductive electrode material. The coatings are heavier adjacent one end of the annulus to facilitate electrical connection thereto. A base is provided which contains two upstanding, slightly conical, ring-shaped conductors which mate with the respective thicker portions of the inner and outer coatings. In a second embodiment electrically conductive leads electrically connect and physically mount the heater within a sealed container, also containing a fusible wax, which container in turn fits closely inside the curler shell.